The present invention relates to the field of machine recognition of magnetically printed characters on a document, and more particularly to a document reader system in which a multiple-gap magnetic read head is used in reading magnetized characters embodying the form of E-13B character fonts printed on a document.
In single-gap magnetic character reading systems, a single analog input waveform is obtained by passing the characters to be sensed, normally printed on a document, beneath a magnetic read head at least as wide as the height of the characters and having a single flux gap. The signal generated by the read head is a derivative waveform representing the rate of change of magnetic flux transversing the head as the characters are scanned. Since the distribution of ink, and thus flux, associated with each different character is unique, the waveform derived for each different character uniquely identifies that character.
In order to increase the amount of information that can be obtained when scanning the magnetically imprinted characters, multiple-gap magnetic read heads have been proposed in which multiple waveforms are produced. Whereas the single-gap read head produces an analog waveform as a result of the D.C. magnetization of the channel to be read, the multiple-gap read head produces a magnetic image of the character as the result of the A.C. magnetization of the characters. Problems found in using a multiple-gap read head lie in the size of the read head compared to the size of the character to be read, together with the failure to print portions of the character during the printing operation. The read head itself consists of thirty separate tracks or channels which cover approximately 0.52 inches of the allowable magnetic ink character recognition (MICR) band. A MICR reader, however, ideally spans about eight tracks (that is, about 0.12 inches). Therefore, every tenth channel is multiplexed together and brought out as a single channel. That is, tracks 1, 11 and 21 are tied together and brought out as channel 1, tracks 2, 12 and 22 are tied together and brought out as channel 2, and so on.
If a MICR character is positioned in the MICR band on a document such that the top of the character crosses tracks 1, 11 and 21 of the read head, then output channels 1-8 inclusive will transmit the signal with channels 9 and 10 blank. In this case, the character scanned in each of the channels is properly orientated. If however, the top of a MICR character crosses track 15, for example, so that it covers tracks 15-22, then output channel 5 will contain the top-of-character signal and output channel 2 will contain the bottom-of-character signal with channels 3 and 4 blank. In this case, the character image is said to be folded. As part of the preprocessing of the data generated by the read head, the image must be unfolded so that it covers channels 1-8 inclusive with channels 9 and 10 blank. As fully disclosed in the co-pending application of Nally et al., Ser. No. 331,936, data is generated identifying the top channel of the character. This data is transmitted to a feature matching unit which matches each row of data of the character with the corresponding row of a plurality of templates associated with known characters in order to obtain information enabling the unknown character to be identified. It is therefore an object of this invention to provide an improved method for matching data representing an unknown character with templates associated with known characters for use in recognizing the unknown character. It is a further object of this invention to provide an apparatus for matching templates with rows of data bits each representing a portion of the character in such a manner as to allow the recognition of the unknown character to take place with a high degree of success.